For instance, in a paper making machine, moisture is removed from wet fiber pulp by pressing it between a pair of opposing rollers, and the surface of such rollers consists of press felt in the form of a relatively broad endless belt. The press felt is made by entangling the fibers of a pad consisting of a plurality of layers of web with ground fabric by needling.
During the weaving process for ground fabric, the warps are set on a warp beam and fed continuously while the weft is supplied by a cop mounted on a shuttle. Therefore, when weaving a relatively broad ground fabric for making press felt, the cop needs to be replaced every time the shuttle has reciprocated a certain number of times through the warps. At the same time, the weft of the old cop needs to be tied, for instance by welding, to the weft of the next cop.
As an automated device for replacing the cop and tying the wefts, there is the one disclosed in the U.S. Pat. No. 5,016,677 (issued May 21, 1991) assigned to the common assignee. The cop changing device includes a shuttle box on each side of the array of warps, a hammer or picking device for transferring a shuttle between the shuttle boxes through a gap between the warps is, a unit for pulling out the shuttle from the shuttle receiving chamber of the shuttle box when replacing the cop, and a robot arm which pulls out the old weft from the old cop and the new weft from the new cop one after the other to a weft tying unit. The robot arm is provided with three distinct hands which are selectively operated according to control commands to replace the old cop with the new cop.
In this device, the bobbin is detachably mounted on the shuttle by being fitted on a tong which can be raised and laid in a-selective manner. When replacing the cop, the shuttle is first of all fixed at a prescribed location, and the bobbin of the old cop is raised and is removed from the tong by the cop clamping hand. Then, a new cop is picked up from a bobbin bin and fitted on a raised tong with the cop clamping hand. The new cop is retracted and mounted into the shuttle so that the weaving process may be resumed.
However, according to this device, the hands for various functions are mounted on a common multi-function arm, and it was therefore difficult to add any hands for new functions to the robot arm. A number of similar functions may be performed by a same hand, but the hand may not be designed to operate in an optimum fashion for each of the functions.